Apparatus for and method of controlling the density of raw materials flowing through a rotary kiln



D. E. SANDBROOK July 7, 1970 APPARATUS FOR AND METHOD OF CONTROLLING THE DENS'IY OF RAW MATERIALS FLOWING THROUGH A ROTARY KILN Filed July 14, 1966 2 Sheets-Sheet l Afforney July 7, 1970 Filed July 14, 1966 PERCENT D. E. sANDBRooK 3,519,815 APPARATUS FOR AND METHOD OF CONTROLLING THE DENSITY 0F RAW MATERIALS FLOWING THROUGH A ROTARY KILN 2 Sheets-#Sheet LJ Asso/v550 95 FREE uur I l l I l I l l Y fab 20 40 60 80 /00 /20 /40 /60 i i F550 No pfff f o/scwzD/rf I l DRY/NG PRE/'EA/NG L CALC/ING BURN/6 4 lof/E `lof/ ZONE Y ZNE DEA/V E 5 s, M

Afro/nay United States Patent O U.s. cl. 25o-43.5 10 claims ABSTRACT OF THE DISCLOSURE This invention relates to rotary kilns, and more particularly to an improved apparatus for and method of controlling the density of material in a rotating kiln. The apparatus for controlling the density of the raw material flowing through a rotary kiln has a frame, a rotatable kiln rotatable on the frame and adapted to receive the raw material at one end and move the raw material through a work zone to the other end, pocket means provided on the periphery of the kiln adjacent a detecting position and adapted to contain raw material and to move along a rotary path of movement, radioactive source means `disposed along the rotary path of movement and operable by movement of the pocket means to direct a beam of radioactive energy through the pocket means and the raw material, detector means disposed adjacent the path of movement and the radioactive source means and adapted to receive radioactive energy transmitted through the raw materialand to convert the radioactive energy into an electrical signal, control means connected to the detector means and actuated by the electrical signal, drive means connected to the kiln and the control means, the control means being operable to change the speed of rotation of the kiln and thereby control the density of the raw material in the kiln.

`Conventional cylindrical kilns are used to manufacture products, such as portland cement clinker, which clinker is produced by heating or roasting of the raw material to promote chemical reactions therein. The kiln is usually driven by a variable speed drive providing an angular velocity in the range of .75 to 3 minutes per revolution depending on the size of the kiln. The slope of the kiln is generally in the order of about l/z inch per foot or slightly steeper. The raw material which is fed into the upper or feed end of the kiln may comprise either dry powder, lter cake containing 18 to 22 percent moisture, or a slurry containing 30 to 50 percent moisture.

In operation the kiln has a drying zone which begins inside the feed end. In a wet process kiln large quantities of chain are suspended from the shell as a heat transfer medium to Vexpedite drying of the kiln feed. In the raw materials preheating zone the raw material or kiln feed is heated to a temperature Where the chemical reactions take place. In the calcining zone the actual pyro-process chemical reactions take place, the calcium carbonates are decomposed and quick lime is produced. In the burning zone the kiln feed is further heated to a temperature where an exothermic reaction takes place producing silicates, aluminates and ferrites. Thereafter, the treated kiln feed or clinker is discharged from the kiln, quenched, cooled and conveyed to storage.

Conventional apparatus for controlling the density of the raw material llowing through a portland cement clinker kiln are of the type shown in the following United States patents: 1,937,094, L. E. Palmer, Nov. 28, 1933; 1,945,652, C. W. Martin, Feb. 6, 1934; 2,303,843, K. R. Knoblauch, Dec. l, 1942; 2,303,910, D. G. Hare, Dec. 15, 1942; 2,316,239, D. G. Hare, Apr. 13, 1943; 2,661,550,

'ice

O. W. Graham, Dec. 8, 1953; 2,722,609, G. W. Morgan et al., Nov. 1, 1955; 2,737,529, P. E. Ohmart, Mar. 6, 1956; 2,763,789, P. E. Ohmart, Sept. 18, 1956; 2,807,523, J. Q. Wood, Sept. 24, 1957; 2,958,777, B. S. Sieswerda et al., Nov. 1, 1960; 2,959,932, P. Spergel, Nov. 15, 1960; 3,011,662, H. R. Dailey, Dec. 5, 1961; 3,060,313, P. E. Ohmart et al., Oct. 23, 1962; 3,070,692, P. E. Ohmart et al., Dec. 25, 1962; 3,075,756, D. H. Gieskieng, Jan. 29, 1963; 3,100,841, J. E. Reider, Aug. 13, 1963; 3,128,786, C. O. Badgett, Apr. 14, 1964; 3,160,745, D. G. Foster, Dec. 8, 1964; 3,164,019, G. M. Burgwald et al., Jan. 5, 1965; 3,180,985, G. I. Leighton, Apr. 27, 1965.

In conventional kilns and conventional control apparatus the llow of kiln feed through the four work zones to insure the required reaction time in each zone is difficult to regulate. The density of the kiln feed is uncontrolled prior to the entry of the kiln feed into the burning zone. Delayed exothermic reaction in the burning zone upsets the kiln heat balance. Reduced kiln production and poor quality clinker are also problems.

OBJECTS OF THE INVENTION It is the general object of the present invention to avoid and overcome the foregoing and other difficulties of and objections to prior art practices by the provision of an improved apparatus for and method of controlling the density of the raw materials flowing through a portland cement clinker kiln, which impoved method and apparatus effectively regulate the flow of kiln feed through the work zones and insures the required reaction time in each zone. Another object is to automatically control the density of kiln feed by automatically regulating kiln velocity prior to entry of the kiln feed into the burning zone. A further object is the elimination of delayed eXothermic reactions in the burning zone. Yet another object is to maintain kiln heat balance. A still further object is to provide maximum kiln production and good quality clinker.

BRIEF SUMMARY O'F THE INVENTION The aforesaid objects of the present invention, and other objects which will become apparent as the description proceeds, are achieved by providing an apparatus for controlling the density of the raw material flowing through e a rotary kiln. The apparatus has a frame and a rotatable kiln rotatable on the frame and adapted to receive the raw material at one end and to move the raw material through a work zone to the other end. Pocket means are provided on the periphery of the kiln adjacent a detecting position and are adapted to contain raw material and to move along a rotary path of movement. Radioactive source means are disposed along the rotary path of movement and operable by movement of the pocket means to direct a beam of radioactive energy through the pocket means and the raw material. Detector means disposed adjacent the path of movement and the radioactive source means are adapted to receive radioactive energy transmitted through the raw material and to convert the radioacive energy into an electrical signal. Control means are connected to the detector means and actuated by the electrical signal. Drive means connected to the kiln and the control means are operable by the control means to change the speed of rotation of the kiln and thereby control the density of the raw material in the kiln.

The invention also contemplates a method for controlling the density of the raw material flowing through a rotary kiln, the method comprising the steps of rotating the kiln and the raw material to move the raw material from one end of the kiln through a work zone to the other end of said kiln; depositing the raw material in a pocket means on the kiln and moving the pocket means and the contained raw material along a rotary path of movement; directing a beam of radioactive energy through the pocket means and the raw material during the rotary path of movement; and receiving the radioactive energy transmitted through the raw material and covering the radioactive energy into an electrical signal. Such method also includes the stops of actuating a control means by the electrical signal and of changing the speed of rotation of the kiln to control the density of the raw material.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS For a better understanding of the present invention reference should be had to the accompanying drawings, wherein like numerals of reference indicate similar parts throughout the several views and wherein:

lFIG. 1 is a side elevational View partially in section of a rotary kiln incorporating the apparatus of this invention;

FIG. 2 is an enlarged fragmentary side elevational View of the apparatus of the present invention;

FIG. 3 is a vertical sectional view taken along the line III-III of FIG. 2 in the direction of the arrows; and

FIG. 4 is a graph showing length of the kiln in feet plotted against percentage of free CaO in the raw material, percentage of radioactive energy transmitted and percentage of radioactive energy absorbed by the raw material.

Although the principles of the present invention are broadly applicable to rotary kilns, the present invention is particularly adapted for use in conjunction with a rotary kiln for the manufacture of portland cement clinker and hence it has been so illustrated and will be so described.

DETAILED DESCRIPTION With specific reference to the form of the present invention illustrated in the drawings, and referring particularly to FIG. l, a rotary inclined kiln of this invention is indicated generally by the reference number and is employed for heat treating a material, such as kiln feed 11.

As shown in FIGS. l, 2, 3 the rotary inclined kiln 10 has an inclined member, such as cylindrical shell 12, which shell 12 extends from a feed house 14 to a burner building 16. Such shell 12 is provided at spaced intervals with reinforcing sleeves 18 and tires 20 which ride on rolls 22 mounted on a frame 24 of the kiln 10. This shell 12 is rotatable in a direction, such as indicated by the arrow in FIG. 1, by drive means, such as girth gear 26 (FIGS. 1, 2), pinion gear 28, gear reduction unit 30 and motor 32. The rotary inclined kiln 10 may be employed to heat treat a material, such as raw material 11 for cement clinker. This raw material 11 is conveyed by a supply means, such as a screw conveyor 36 (FIG. 1), from the feed house 14 into a feed means 38, disposed adjacent the shell inlet to a drying zone for introduction of the raw material 11 into the rotary kiln 10. This raw material or kiln feed 11 may comprise crushed limestone, shale, sand and iron ore. The feed means 38 may comprise, by way of example, a stationary housing 40 disposed about the outer shell 12 and having an inlet 42 from the screw conveyor 36.

Referring to FIGS. 2 and 3, the apparatus for controlling the density of the raw material 11 flowing through the rotary kiln 10 has in addition to the frame 24, the shell 12 rotatable on the frame 24 as described above. This shell 12 is adapted to receive the raw material 11 at the left hand end, as viewed in FIG. l, and move such raw material 11 through work zones, such as the drying zone, preheating zone, calcining zone, burning zone, and quenching and discharging Zone to the other or right hand end (FIG. 1) of the kiln 10.

Pocket means, such as the pocket 44 (FIGS. 1 3), may be provided on the periphery of the shell 12 at a plurality of points along the length L (FIG. l) of the kiln 10. For purposes of illustration one such pocket 44 has been shown in FIGS. 1-3 in the calcining zone. The pocket 44 is adapted to contain raw material 11 and moves along a rotary path of movement indicated by the arrows in FIGS. l and 3. Such pocket 44 has a width Wp in the range of about 3.0-12.0 inches, a length Lp-to-width Wpto-depth Dp ratio of about 2 to 1 to l and is generally rectangular in horizontal cross section.

A radioactive source means, such as the radioactive source 46 of the type manufactured by Industrial Nucleonics Corporation, Columbus, Ohio, as a Model LS102 or of the type manufactured by the Ohmart Corporation, Cincinnati, Ohio, as `a Caesium 137 or Cobalt 60 Source, is mounted on a bracket 48 upstanding from the frame 24 along the rotary path of movement of the pocket 44. Switch means, such as a normally open microswitch 50, connected to the radioactive source 46, is operable by the pocket `44 to close and to cause the source 46 to direct a beam of radioactive energy through the pocket 44 and the raw material 11 in the pocket 44. Such penetrative radiation may be selected from the group consisting of X-rays, gamma rays, beta rays and neutrons.

A detector means, such as a Geiger Mueller type detector 52 (FIG. 3) of the type produced by the Ohmart Corporation or Industrial Nucleonics Corporation, is disposed adjacent the rotary path of movement of the pocket 44 and the radioactive source 46 on a bracket 54 and is adapted to receive radioactive energy transmitted through the raw material 11 and to convert such transmitted radioactive energy into a measurable electrical signal. The detector 52 usually contains two electrodes (not shown) separated by a filling gas, `which gas is ionized by exposure to the nuclear radiation. Positive ions are attracted to the positive electrode (not shown), thus generating an electrical current in the detector 52.

Control means, such as the controller 56 of the type manufactured by Leeds-Northrup, Philadelphia, Pa., is mounted at 58 (FIG. 3) and connected by leads 60a, 60h to the detector 52 and by conductors 62a, 62b to the motor 32 of the drive means. Such controller S6 is actuated by the electrical signal produced by the detector 52 and is operable to change the speed of rotation of the kiln 10 thereby controlling the density of the raw material 11 in the kiln 10.

As hereinafter mentioned the drive means includes the motor 32, gear reduction unit 30, pinion gear 28 and girth gear 26.

It will be understood by those skilled in the art that amplifier means, such as a simple bridge-type amplier 64 (FIG. 3) of the type manufactured by the Ohmart Corporation, is mounted at 66 and is connected between the detector 52 and the controller 56 for amplifying the electrical signal from the detector 52. The amplifier 64 has a vacuum tube (not shown) in one arm of the bridge (not shown) and is provided with temperature regulation for the electrometer tube and input load resistor (not shown).

It has been found that the raw material 11 should have a density in the range of 1200-1800 grams/liter. The kiln 10 should rotate at a peripheral speed in the range of 7.0-l4.0 inches/second and have a diameter in the range of l0-18 feet. The detector 52 is provided with a measure time of about 1.5-3.5 seconds and the spacing between the radioactive source 46 and detector 52 is in the range of 3.0-l3.0 inches. Under these conditions the results shown in FIG. 4 achieve the objects of the present invention.

METHOD It will be understood from the above description of the apparatus that an improved method of controlling the density of the raw material 11 in the kiln 10 has been provided. This method comprises the steps of rotating the kiln 10 and the raw material 11 to move the raw material 11 from one end of the kiln 10 through work zones (such as the drying zone, raw material preheating zone, calcining Zone and burning zone) to the other end of the kiln depositing the raw material 11 in a pocket 44 and moving the contained raw material 11 along a rotary path of movement; directing a beam of radioactive energy through the pocket 44 and raw material 11 during the rotary path of movement; and receiving the radioactive energy transmitted through the raw material 11 and converting the radioactive energy into an electrical signal. Thereafter, are the steps of actuating a control means 56 by the electrical signal and changing the speed of rotation of the kiln 10 to control the density of the raw material 11.

SUMMARY OF THE ACHIEVEMENT OF THE OBI ECTS OF THE INVENTION It will be recognized by those skilled in the art that the objects of the present invention have been achieved by providing an improved apparatus (FIGS. l-3) for and method of controlling the density of the raw materials 11 ilowing through a portland cement clinker kiln 10, which improved method and apparatus effectively regulate the flow of kiln feed 11 through the work zones and insures the required reaction time in each zone, automatically control the density of kiln feed 11 by automatically regulating kiln velocity prior to entry of the kiln feed 11 into the burning zone, eliminate delayed exothermic reactions in the burning zone, maintain kiln heat balance, and provide maximum kiln production and good quality clinker.

While in accordance with the patent statutes preferred and alternative embodiments of the present invention have been illustrated and described in detail, it is to be particularly understood that the invention is not limited thereto or thereby.

I claim:

1. Apparatus for controlling the density of the raw material iioWing through a rotary kiln, said apparatus comprising (a) a frame,

(b) said rotary kiln rotatable on said frame and adapted to receive said raw material at one end and move said raw material through a work zone to the other end,

(c) pocket means provided on the periphery of said kiln adjacent .a detecting position and adapted to contain raw material and to move along a rotary path of movement,

(d) radioactive source means disposed along said rotary path of movement,

(e) switch means adjacent said rotary path of movement, connected to said radioactive source means and operable by movement of said pocket means to cause said radioactive source means to direct a beam of radioactive energy through said pocket means and said raw material,

(f) detector means disposed adjacent said path of movement and said radioactive source means and adapted to receive radioactive energy transmitted through said raw material and to convert said radioactive energy into an electrical signal,

(g) control means connected to said detector means and actuated tby said electrical signal, and

(h) drive means connected to said kiln and said control means, said control means being operable to change the speed of rotation of said kiln and thereby control the density of said raw material in said kiln.

2. The apparatus recited in claim 1 and having amplier means connected to said detector means for amplifying said electrical signal.

3. The apparatus recited in claim 1 wherein said kiln has a diameter in the range of 10-18 feet.

4. The apparatus recited in claim 1 wherein said raw material has a density in the range of 0-1800 grams/ liter.

5. The apparatus recited in claim 1 wherein said kiln has a peripheral speed in the range of 7.0-14.0 inches/ second.

6. The apparatus recited in claim 1 `wherein said pocket means has a length-to-width-to-depth ratio of about 2 to 1 to l.

7. The apparatus recited in claim 1 wherein detector means has a measure time in the range of about 1.5-3.5 seconds.

:8. A method for controlling the density of the raW material flowing through a rotary kiln, said method comprising the steps of (a) rotating said kiln and said raw material to move said raw material from one end of said kiln through a work zone to the other end of said kiln,

(b) depositing said raw material in a pocket means on said -kiln and moving said pocket means and said contained raw material along a rotary path of movement,

(e) 'actuating a switch means disposed adjacent said rotary path of movement and connected to a radioactive source means by said pocket means to direct a beam of radioactive energy from said radioactive source means through said pocket means and said raw material during said rotary path of movement, and

(d) receiving the radioactive energy transmitted through said raw material and converting said radioactive energy into an electrical signal.

9. The method recited in claim 8 and including the step of actuating a control means by said electrical signal.

10. The method recited in claim 9 and including the step of changing the speed of rotation of said kiln to control the density of said raw material.

References Cited UNITED STATES PATENTS 2,565,963 8/ 1951 Graham.

FOREIGN PATENTS 151,054 19612 U.S.S.R.

RALPH G. NILSON, Primary Examiner M. J. FROME, Assistant Examiner U.S. C1. X.R. Z50-83.3

UNITED STATES PATENT QFFICE CERTIFICATE 0F CRRECTON Patent No. 3,519,815 July 7, 1970 Dean E. Sandbrook It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 71, "2,303,910" should read 2,304,910

Column 2, line 59, "acve" should read active Column 3, line 5, "covering" should read converting line 6, "stops" should read steps line 57, cancel "shell". Column 4, line ll,

after "46" insert (Figure 3 line 46, "hereinafter" shbuld read herenbefore Signed and sealed this 16th day of February 1971.

(SEAL) Attest:

Edward M. Fletcher, Jr. WILLIAM E. SCHUYLER, JR.

Attesting Officer Commissioner of Patents 

